Transfer inks for duplication processes



United States Patent TRANSFER INKS FOR DUPLICATION PROCESSES RoyClifford Locke, Salem, N. .L, assignor to E. I. du Pont de Nemours andCompany, Wilmington, DeL, a corporation of Delaware No Drawing.Application January 8, 1954, Serial No. 403,059

9 Claims. (Cl. 106-22) This invention relates to transfer inks forduplication processes. More particularly, this invention deals withnovel oily compositions of matter adapted for use as the color bearingliquid in the manufacture of typewriter ribbon. This invention furtherembraces the novel typewriter ribbons thus produced.

It is an object of this invention to provide transfer inks of theaforegoing character which are essentially colorless in themselves or atleast have no great tendency to produce intensely colored stains uponthe fingers of a person, while yet being adapted to produce, through themedium of a typewriter ribbon, an intensely colored message on a sheetof paper. A further object of this invention is to produce anessentially non-staining typewriter ribbon of the character and for thepurposes aforementioned. Various other objects and achievements of thisinvention will become apparent as the description proceeds.

When I speak of essentially colorless typewriter ribbon in thisspecification, it will be understood that I am referring to the film ofthe oily ink which permeates the typewriter ribbon, not to the articleas a whole. For clearly, it is possible to use for the background itselfa dyed ribbon, without stepping out ofthe teachings of this invention.In other words, my principal object in this invention is to producearticles of manufacture of the character and for the purposes mentioned,in which that component which normally rubs ofi onto a persons handsshall be essentially colorless or non-staining. It follows further thatabsolute freedom from color is not essential to this invention, inasmuchas the purpose may be fully satisfied even if the oily liquid is weaklybuff colored or dark, so long as it does not produce an objectionableand tenaciously adhering stain upon the fingers.

The current general practice in duplication processes, such as thespirit hectograph process, impact-printing and ordinary typing withcarbon copies, is discussed at length in copending application of WalterJean Balon and Otto Stallmann, Serial No. 400,776, filed December 28,1953. The noxious problem of staining arising from the customary use insaid practice of polyalkyl triaminotriphenyl methane colors isalso'discussed there in detail. The term polyalkyl there is defined asindicating the presence of not less than and not more than 6 lower alkylradicals per molecule, wherein lower alkyl is typified by methyl tobutyl. It will be used in the same sense throughout the instantspecification and claims. As common commercially available illustrationsof the colors in question are mentioned methyl violet, crystal violetand ethyl violet.

Balon and Stallmann then describe and claim novel, essentially colorlesscompositions of matter comprising the carbinol form ofN-polyalkyl-tri(p-aminophenyl) methane colors in intimate associationwith a relatively smaller quantity of quaternary ammonium bases whichcontain alkyl, aralkyl, cycloalkyl, hydroxyalkyland epihydrin groupsintheir structure, as typified by benzyl-trimethylammonium hydroxide andseveral other compounds named in said specification.

The compositions are prepared by heating the normally highly colored,commercial carbinol form of one of the aforementioned colors, in asecondary or tertiary alcohol which contains an excess of the mentionedquaternary base, until the intense blue color disappears, and thencooling and isolating the colorless crystals of the carbinol whichpresumably contain occluded quaternary base. The isolated solid issufiiciently retarded as to color development, to permit its handling inthe various processes involved, such as filtration and drying, and topermit its storing for a few days or weeks.

As specific illustrations of their invention and mode of procedure saidcopending application of Balon and Stallmann brings numerous detailedexamples; including Example 1 which reads as follows:

To a stirred mixture of 50 g. of crude crystal violet carbinol in 3700cc. of isopropyl alcohol at room temperature, 10 cc. of a commercialaqueous solution (36%) of benzyl trimethyl ammonium hydroxide wereadded. The mixture was stirred and heated during 45 min. to refluxtemperature (82 C.), and held under reflux until completely discolored(about 1 hr.). The resulting pale yellow solution, after filtering atabout C. and cooling, gave the product in the form of long, white,orthorhornbic prisms which melted at 194 C. to 196 C. These crystalsanalyzed 11.4% N; (theoretical is 10.8% They were characterized byunusual stability to color change, a sample having remained colorlessfor over 4 months when kept in a glass jar which was opened frequently.

A product of the same quality was obtained when the hot filtration wasomitted. Likewise, the use of 15 cc. and 25 cc. of the quaternaryammonium base gave the same results.

Other carbinols and dyestuffs specifically named in said copendingapplication of Balon and Stallmann and treated by the general processtherein set forth are Crystal violet itself (Col. Ind. 681);

Ethyl violet (Col. Ind. 682);

N-hexa(n-butyl -tri(p-aminophenyl) -carbinol, obtained by condensing 2moles of N-di-n-butyl-aniline with 1 mole ofp-(di-n-butyl-amino)-benzaldehyde, followed by oxidation with chloranil.

N-tetra(n-butyl)-N-diethyl tri(p aminophenyl) carbinol, obtained insimilar manner except using p-diethylamino-benzaldehyde.

Other quaternary ammonium hydroxides named in said copending applicationare tetrarnethyl-ammonium hydroxide, phenyl-dimethyl-benzyl-ammoniumhydroxide, N-methyl-pyridinium hydroxide and the reaction product ofepichlorhydrin and ammonia produced according to U. S. P. 1,977,251.

Balon and Stallmann further found that the mentioned colorless carbinolcomposition may be further stabilized against discoloration in longstorage or upon exposure to a humid atmosphere rich in CO2 fumes, bycoating the crystals with a fatty substance such as carnauba wax,provided the natural, residual acidity of the Wax is first neutralizedby treatment with a quaternary base of the type hereinabove discussed.

The invention of Balon and Stallman is very useful in that it producesfor the first time a composition of matter readily transformable into atriphenyl methane color, yet free of color itself and free of theinevitable nuisance normally attendant upon the handling and use ofthese colors in spreading intensely colored dusts and in producingdifficultly removable stains upon the hands and clothes of persons. Thesaid invention is also very elfective insofar as its primary object ofhandling, storing and using the coloring agent per se is concerned.Samples of the coated, colorless carbinols, produced according to Balonand Stallmann, have been known to resist discoloration for many months,even when kept in the vicinity of a large chemical plant, wherein theatmosphere is apt to be laden with various acid fumes.

The color stability of the Balon and Stallmann product, however, appearsto be dependent upon its crystalline form. When the product is dissolvedin or ground into an oily vehicle which is then spread out through thefiber of a typewriter ribbon, the color stability essentiallydisappears. In other words, colorless typewriter ribbon prepared fromthe colorless carbinol composition of Balon et al. are not so stable todiscoloration in storage or upon exposure to the atmosphere as is thecrystalline coloring agent itself. Perhaps the thinness of the film andthe high surfaceto-volume ratio of the ground carbinol particle arecontributing factors to this reduced discoloration stability.

Now according to my invention, the above problem is solved, and stablethin films of essentially colorless N- polyalkyl-tri(p-aminophenyl)carbinols are produced by adding to the coating-ink composition, inaddition to its customary vehicle and the mentioned coloring agent, arelatively large proportion of an organic nitrogenous base whosephysical state is selected to match the vehicle of the ink composition,in view of its intended use. In other words, inasmuch as the vehiclegenerally selected for impregnating typewriter ribbon is of an oily orliquid nature, I select as nitrogenous base an aliphatic amine which isliquid at room temperature, but boils above 150 C. Other practicalrequisites are freedom from objectionable odor and color and absence oftendency to polymerize.

Practical examples of such oily amines, suitable for the purposes ofthis invention are mono-, diand triethanolamine, tri-n-propylamine,tri-isobutylamine, di-n-butylamine, nor iso-octylamine, hexamethylenediamine, diethylene triamine, triethylene tetramine and tetraethylenepentamine.

The preferred quantity of the mentioned third ingredient is preferablybased on the weight of the entire ink rather than on its coloringconstituent. It may vary from 5 to 50% by weight of the entirecomposition. For practical purposes, however, I prefer to use a quantityof the amine equal to from 20 to 40% by weight of the entirecomposition.

It is noteworthy, that this is the first time in my experience that acoating ink for a transfer medium is finishcd on the alkaline side.Hitherto, the triphenyl methane colors themselves have been employed,for instance methyl violet, crystal violet or ethyl violet. These beingsalts, more particularly chlorides, care has always been taken toproduce a coating ink composition of acid reaction. My novelcompositions, however, when tested by dissolving a sample in aqueousalcohol, are alkaline to Brilliant Yellow. This test may indeed be takenas defining the lower limit of said third ingredient in my novel inkcompositions.

The mode of incorporation of the several ingredients with each other isnot critical. The colorless carbinol composition may be incorporatedinto the mixture of vehicle and base by grinding on an ink mill, or thecarbinol composition may be dissolved in a solvent such as benzene, thenadded to the oily vehicle and base mixture, whereupon the resultingcomposition may be sprayed onto the ribbon. To my knowledge, the lattermode of incorporating the coloring agent is also novel.

In other details, the mode of preparing the typewriter ribbon, mayfollow customary practice in this art.

Without limiting this invention, the following examples are given toillustrate mypreferred mode of procedure. Parts mentioned are by weight.

Example 1 Materials: Parts White mineral oil (Nujol") 71.4Monoethanolamine 25.7

Colorless carbinol composition from the above reproduced Example 1 ofcopending application of Balon and Stallmann, Ser. No.

Total 100.0

Mix the ingredients together thoroughly by stirring 15 minutes at roomtemperature. Grind by passing 6 times through a three roll ink mill.Coat on typewriter ribbon in the usual manner.

The pure white ink and ribbon thus obtained stays uncolored duringlengthy storage periods and does not stain the hands objectionably. Atypewritten impression on a copy sheet which had a natural acidity dueto acid aluminum compounds incorporated in its manufacture, developed toa good lcgibility in 20 minutes. The intensity of the impression thenprogressively increased to a very strong copy after 2 hours.

Example 2 Use the materials same as in Example 1, except substitute lardoil for the mineral oil.

The pure white ink obtained develops to the colored copy impression morereadily than does the product of Example 1.

Example 3 Same materials as in Example 1, except substitute castor oilfor the mineral oil.

The pure white copy ink is much more readily developed under identicalconditions or by heat than the inks of Examples 1 and 2, but stillpossesses remarkably superior properties over the prior art products.

Example 4 Materials: Parts Lard oil 14.6 Castor oil 26.3Monoethanolamine 17.5 Coloring agent as in Example 1 41.6

Total 100.0

possesses the advantage of cleaner handling properties than theconventional hectograph ribbons in which basic dye chlorides have beenused as the color component.

Example 5 Materials: Parts White mineral oil 35.7 Monoethanolamine 12.8Coloring agent as in Example 1 2.5 Benzene 49.0 Total 100.0

Dissolve the color ingredient in the benzene by stirring at roomtemperature. Add the remaining two components. Stir well. Run thetypewriter ribbon through the colorless solution. Squeeze to apracticable dryness. Allow to stand overnight in order to evaporate thebenzene.

The above solution can also be applied to the ribbon by spraying througha pressure gun.

The pure-white, inked ribbon obtained is stable against colordevelopment while on the ribbon. When transferred by impact to copysheets of sufiiciently high acidity, copies of readable intensity areobtained immediately.

A further advantage is the elimination of the grinding operation.

Example 6.C0ating hot Add all the ingredients together. Heat to 200 C.with good agitation and maintain this temperature until a colorlessclear solution is obtained. Immerse the ribbon in the clear solution.Withdraw the ribbon after complete impregnation is reached and squeezeas dry as practicable.

The ribbon thus obtained is suitable for use in preparing the mastersheet for hectograph duplication. The pure-white ink impregnated in theribbon remains colorless until contacted with acid media.

The hot application technique of this example attains the advantage ofeliminating the grinding operation in the preparation of the colorlessink. The ink of this example can also be applied by spraying the samefrom a heated pressure gun, at 200 C., directly onto the ribbon fabric,and then passing the latter over heated rolls at the same temperature.

It will be understood that the details of the above examples may bevaried within wide limits. Thus in lieu of the particular colorlesscarbinol named in each example any other of the products mentioned insaid copending Balon and Stallmann application, or their equivalents,may be employed, for instance, tri-(p-diethylaminophenyl) carbinol,tri-(p-n-propylaminophenyl) carbinol, di (p dimethylaminophenyl) pdiethylaminophenylcarbinol.

The first of these will be recognized as the carbinol of ethyl violet.The other two are not at present commercial products, but were preparedspecially for these tests by the mentioned inventors.

In lieu of the oils or oil-mixtures indicated in the above examples, anyother non-drying oil or mixture of oils customarily employed in the artas vehicles for typewriter ribbon inks may be employed in thisinvention. The oily vehicle may also be modified by adding theretoplasticizers or agents for controlling their hygroscopicity. Solid orwaxy amines, for instance stearylamine or some of the other amines namedin the copending application of T. G. Webber and Roy C. Locke, SerialNo. 403,040 (of even date herewith), may be added in limited proportionsto adjust the consistency of the ink composition, if desired.

The quantity of colorless carbinol incorporated into the coating inkformulation, will naturally vary according to the purpose of the ink,but may otherwise follow the corresponding practice in the art whenusing the colored dyes. In other words, for ordinary typing, thequantity of coloring agent is generally from 1 to by weight of theentire coating ink. But for preparing master sheets for hectographprinting, 10 to 50% by weight is the quantity of coloring agent commonlyused in the typewriter ribbon.

Because of the remarkable stability of the colorless coatings in thetransfer sheets and ribbons hereinabove discussed, it is necessary thatthe paper upon which the copy is to be developed should come in contactwith acidic agents during the development stage. In the case ofhectograph duplication in a rotary machine using an alcoholic moisteningagent, the acidic agent can be readily added to the moistening fluid. Inthe case, however, of typing from one of the aforegoing typewriterribbons it is desirable that the paper itself have an acid reaction.

Many commercial papers have a natural acid reaction by virtue of clays,aluminum silicates or' acid-reacting salts incorporated into the paperfiber during manufacture. On the other hand, paper intended for use withthe typewriter ribbons of this invention, may be treated with certainacids, whereby to give it a weak acid reaction. The treatment willusually consist of impregnating the paper with an aqueous, alcoholic, oraqueousalcoholic solution of an organic acid, and allowing the vehicleto evaporate. As organic acid is preferably chosen one which is solid atroom temperature, soluble in water, alcohols or mixtures of the two, hasno color of its own and is free from bad odors or toxicity. As examplesof suitable acids may be mentioned acetic, oxalic, citric, tartaric,benzoic, salicylic, pyr'ogallic, naphthalene sulfonic, p-tolue'nesulfonic, and various others.

Moreover, it has been observed that the shade of the color developedupon the copy paper can be varied to some extent by the choice of theacid. Thus, using the carbinol of crystal violet as coloring agent,stearic, citric and tartaric acids developed purple impression; oxalicacid gives a blue; and pyrogallic acid gives a jet black.

The speed of color development also can be varied to some extent by thechoice of acid. Of the acids tested by me thus far, citric, tartaric andsalicylic develop most rapidly and give intensely colored imprints.

The following additional examples will illustrate the preparation anduse of such acidic paper, insofar as it is pertinent to my presentinvention.

Example 7 A sheet of white paper is impregnated With a 5% solution ofoxalic acid in alcohol and allowed to dry thoroughly under normalconditions.

A record made on this paper using the typewriter ribbon of Example 1above, develops a strong violet shade immediately after typing. Thisintensity increases somewhat during the next 24-hour period. Thereafer aprogressive shade-change takes place to an ultimate black impression.

Example 8 The procedure is the same as in Example 7, except that citricacid is used in place of oxalic acid.

The treated paper thus obtained gives a violet copy which is many timesstronger within 15 minutes than the untreated sheet gives after severaldays.

It is distinguished over the product of Example 7 by a more rapiddevelopment of a high intensity print, which does not change its violetshade in storage.

Essentially similar results are obtained with paper which had beenimpregnated with any of the other acids named above, except for theindividual differences in rate of color development and ultimate shade,as already noted above. In the case of tannic acid, a special furtherimprovement obtained in that the impression is non-bleeding in water.That is, water flowed over the sheet shows no evidence of bleed from theletters into the adjacent uncolored areas.

Numerous other changes and variations in the details of my inventionwill be readily apparent to those skilled in the art.

I claim as my invention:

1. An ink composition for producing non-staining typewriter ribbons,comprising an oily ink vehicle and a color producing agent, said colorproducing agent comprising the carbinol of anN-polyalkyl-tri(p-aminophenyl) methane dye in a state of purityessentially free of the corresponding color, and said ink compositioncomprising further a nitrogenous organic base which is miscible withsaid oily vehicle, said base being a non-drying aliphatic amine which isliquid at room temperature but does not boil below C., said base beingpresent in quantity not less than 5% and not greater than 50% by weightof the entire composition.

2. An ink composition as in claim 1, the organic nitrogenous base beingan alkylamine.

3. An ink composition as in claim 1, the organic nitrogenous base beingan alkylolamine.

4. An ink composition as in claim 1, the organic nitrogenous base beinga polyalkylene-polyamine.

5. A composition of matter as in claim 1 the quantity of said colorproducing agent being from 1 to 10% by weight of the entire composition.

6. A composition of matter as in claim 1 the quantity of said colorproducing agent being from 10 to 50% by weight of the entirecomposition.

7. The process of preparing an ink composition adapted for producingnon-staining typewriter ribbon, which comprises incorporating into anoily ink-vehicle a coloring agent and an organic nitrogenous base, saidcoloring agent being the carbinol of an N-polyalkyl-tri(p-aminophenyl)methane dye in a state of purity essentially free of the correspondingcolor, and the nitrogenous base being an amine which is liquid at roomtemperature but does not boil below 150 C., the quantity of said basebeing not less than 5% and not more than 50% by weight of the entirecomposition.

8. The process of preparing a non-staining typewriter ribbon for typingwith acidic paper, which comprises impregnating a textile ribbon with anink composition comprising an oily vehicle, a coloring agent and anorganic nitrogenous base, the coloring agent being the carbinol of anN-polyalkyl-tri(p-aminophenyl) methane color in a state of purityessentially free of the corresponding color, and the nitrogenous basebeing a compound which is liquid at room temperature and is misciblewith said oily vehicle, the quantity of said base being from 5 to andthe quantity of coloring agent being from 1 to 50% by weight of the inkcomposition.

9. A non-staining typewriter ribbon comprising a textile ribbonimpregnated with a basic, essentially colorless, ink composition asdefined in claim 8.

References Cited in the file of this patent UNITED STATES PATENTS1,198,442 Hochstetter Sept. 19, 1916 2,306,863 Bour Dec. 29, 19422,392,658 Geopfert Jan. 8, 1946 2,427,921 Pfaelzer Sept. 23, 1947

1. AN INK COMPOSITION FOR PRODUCING NON-STAINING TYPEWRITER RIBBONS,COMPRISING AN OILY INK VEHICLE AND A COLOR PRODUCING AGENT, SAID COLORPRODUCING AGENT COMPRISING THE CARBINOL OF ANN-POLYALKYL-TRI(P-AMINOPHENYL) METHANE DYE IN A STATE OF PURITYESSENTIALLY FREE OF THE CORRESPONDING COLOR, AND SAID INK COMPOSITIONCOMPRISING FURTHER A NITROGENOUS ORGANIC BASE WHICH IS MISCIBLE WITHSAID OILY VEHICLE, SAID BASE BEING A NON-DRYING ALIPHATIC AMINE WHICH ISLIQUID AT ROOM TEMPERATURE BUT DOES NOT BOIL BELOW 150* C., SAID BASEBEING PRESENT IN QUANTITY NOT LESS THAN 5% AND NOT GREATER THAN 50% BYWEIGHT OF THE ENTIRE COMPOSITION .